How to lower boost with a internal waste gate.
When a normally aspirated engine is turbo'd, you usally want to start with the lowest boost pressure possible, most OEM turbo's with a internal waste gate are set to 8psi. That's fine if your your confident in your tuning, but with just a FMU for engine managment 8psi can be too much. A Boost Controller can only raise the pressure above what the waste gate spring is set to, the waste gate needs to be modified to open at lower psi. There are 4 main way's to do this, Spring Swap, Rod Lengthening, Choke Spring, or Push Back Spring. Some have there advantages and disadvantages.

Spring Swap

Tools needed, ^cutter as shown, possibly a grinder and welder.

To split the waste gate, you need to locate the seem and fold back the crimped edge. I needed to grind off the rod were it was mushroomed over the spring cap. After the new spring was installed I then spot welded the rod back on the spring cap.

I used the softer set of springs that came in my Ebay Greddy knock off BOV. They were a perfect fit and run 5.5psi.

Now my BOV needed a new spring, and the old waste gate spring seemed too hard. So I used a spring from a old EGR valve from a Ford. It's shorter, but since the BOV is adjustable I can crank it all the way down, seems to hold boost fine. Now I can just use a regular boost controller to increase the boost when I'm ready.

Rod Lengthening

Works good to a certain point. If your setting it for really low boost, the flapper door may not close competely and cause a slow spool. You can also adjust the rod tighter to increase boost.

Choke Spring

Look close between the turbo and radiator
With this mod you disconnect the waste gate actuator rod completely from the flapper. Now just use what's commonly called a "Choke Spring" to hold the flapper shut. Thats it, simple is'nt it? For more boost pull the spring back, for less move it closer for less pressure. It works well for not having a actuator open the flapper, just the exshaust pressure opens it. I had a hard time gettin exsactly what I wanted, and would spike when cold. If your in a hurry to get boosted, this will get you going.

Push Back Spring

Photo stolen courtesy of MK96
You dont have to open the actuator to do this mod, leave the spring in the waste gate, but add one as shown. You can adjust the exsternal spring to adjust boost. Because of the bends and shape of the T25 waste gate rod, I was'nt able to do this.